System and method for energy recovery

ABSTRACT

The present disclosure relates to an energy recovery system for a vehicle powered by an engine. The energy recovery system includes a thermoelectric module which is interfaced with a heat source of the vehicle. The heat source generates waste heat. Further, the waste heat provides a high temperature heat source for the thermoelectric module. A low temperature heat source is also interfaced with the thermoelectric module. A temperature difference between the high temperature heat source and the low temperature heat source generates thermoelectric power. A controller is configured to control a parameter of the engine to maintain an optimal value of the temperature difference between the high temperature heat source and the low temperature heat source.

TECHNICAL FIELD

The present disclosure relates to a system and a method for energy recovery, and more specifically to a system and a method for generating electrical energy from waste heat in a vehicle.

BACKGROUND

Vehicles powered by an engine are well known in the art. In some cases, the engine may be coupled with an electric generator. The electric generator may provide power to various electrical equipment of the vehicle. The engine may also provide power directly to one or more components of the vehicle.

The engine produces power by combusting a mixture of air and fuel. The engine generates an exhaust as a byproduct of combustion. The exhaust may be discharged after passing through the one or more turbochargers. Consequently, a heat associated with the exhaust may be wasted. Therefore, an efficiency of the vehicles may get reduced.

U.S. Published Application Number 2005268955 discloses a locomotive diesel engine waste heat recovery system for converting waste heat of engine combustion into useful work. A thermoelectric module is connected to the hot engine exhaust to provide a high temperature heat source, and the engine coolant system is also connected to the thermoelectric module to provide a low temperature heat source. The difference in temperature of the heat sources powers the thermoelectric module to convert waste heat of the engine into electricity to power selected devices of the locomotive.

SUMMARY OF THE DISCLOSURE

In one embodiment of the present disclosure, an energy recovery system for a vehicle is provided. The energy recovery system includes a thermoelectric module which is interfaced with a heat source of the vehicle. The heat source generates waste heat. Further, the waste heat provides a high temperature heat source for the thermoelectric module. A low temperature heat source is also interfaced with the thermoelectric module. A temperature difference between the high temperature heat source and the low temperature heat source generates thermoelectric power. A controller is configured to control a parameter of the engine to maintain an optimal value of the temperature difference between the high temperature heat source and the low temperature heat source.

Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary vehicle, according to an embodiment of the present disclosure;

FIG. 2 is a schematic illustration of an energy recovery system of the vehicle, according to an embodiment of the present disclosure;

FIG. 3 is a schematic illustration of a thermoelectric module, according to an embodiment of the present disclosure; and

FIG. 4 illustrates a method of energy recovery heat in the vehicle, according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts. Referring to FIG. 1, an exemplary vehicle 100 is illustrated. Specifically, the vehicle 100 may be a locomotive. Alternatively, the vehicle may be a diesel-electric multiple unit.

The vehicle 100 includes a power source 102 (shown schematically). As shown in the illustrative embodiment of FIG. 1, the power source 102 may include an engine 104 coupled to an electric generator 106. In an alternative embodiment, the engine 104 may be coupled to a mechanical transmission, hydraulic transmission, a pneumatic transmission, or a combination thereof. The engine 104 may also provide power to other components of the vehicle 100. The engine 104 may be an internal combustion engine or a gas turbine. In one embodiment, the engine 104 may be a diesel engine. The electric generator 106 may provide power to various electric equipment of the vehicle 100 including a drive system (shown schematically in later figures) and an auxiliary system (shown schematically in later figures) of the vehicle 100. The drive system may include multiple traction motors (not shown) configured to drive respective axles 108. The axles 108 are coupled to a pair of wheels 110 which run on rails 112.

The engine 104 combusts fuel and produces power for running the vehicle 100. In the process, the engine 104 also produces waste heat. An energy recovery system 200 (explained with reference to FIG. 2) may be provided to recover at least a portion of the waste heat produced by the engine 104. A residual waste heat may be rejected to atmosphere 201.

FIG. 2 illustrates a schematic view of the energy recovery system 200, according to an embodiment of the present disclosure. As illustrated in FIG. 2, an exhaust conduit 114 is associated with the engine 104 in order to convey an exhaust 116. The exhaust 116 may pass through one or more turbochargers (not shown). A portion of the exhaust 116 may also be recirculated back to the engine 104 via an exhaust gas re-circulator (not shown).

The exhaust 116 is interfaced with a thermoelectric module 202. In one embodiment, the exhaust 116 is interfaced with a thermoelectric module 202 after passing through the one or more turbochargers. The exhaust 116 may contact a high temperature side 204 of the thermoelectric module 202. Waste heat associated with the exhaust 116 may provide a high temperature heat source TH for the thermoelectric module 202. The exhaust 116 may provide a heat QH to the high temperature side 204 of the thermoelectric module 202. The exhaust 116 may be then discharged into atmosphere 201. Thus, the thermoelectric module 202 may recover the heat QH, which would otherwise have been rejected as waste heat to atmosphere 201. Further, the thermoelectric module 202 includes a low temperature side 206 which is interfaced with a low temperature heat source TL. The low temperature heat source TL may extract a heat QL from the low temperature side 206 of the thermoelectric module 202. In various embodiments, the low temperature side 206 may include ambient air, a cooling system (not shown) associated with the engine 104, a secondary cooling system (not shown) associated with the thermoelectric module 202, or a combination thereof. The thermoelectric module 202 may provide a thermoelectric power PT due to a temperature difference DeltaT between the high and low temperature heat sources TH and TL. The thermoelectric power PT may be in the form electric power and conveyed by electric connections 208.

In the exemplary embodiment of FIG. 2, the exhaust 116 is shown as a heat source that generates waste heat. However, there may be other heat sources, for example, a hot side of the cooling system associated with the engine 104, a dynamic brake grid (not shown), an aftercooler (not shown), an intercooler (not shown), traction motors, the electric generator 106 etc.

In an embodiment, an engine controller 209 may control various parameters of the engine 104. The engine controller 209 may receive input signals from multiple sensors (not shown) associated with the engine 104. The engine controller 209 may control the parameters of the engine 104 based on the input signals from the multiple sensors and lookup tables. The parameters of the engine 104 may include, for example, but not limited to, an engine speed S, air/fuel ratio, ignition timings, valve timings etc.

As shown in FIG. 2, the engine 104 is drivably coupled to the electric generator 106. The engine 104 may generate a power output PM. The power output PM of the engine 104 may depend on various parameters of the engine, for example, but not limited to, the engine speed S, rate of fuel supply etc. At least a part of the power output PM of the engine 104 may be used for driving the electric generator 106. In an embodiment, the electric generator 106 may be an alternator, which generates an electrical power PA in the form of alternating current. However, in alternative embodiments, the electric generator 106 may be a dynamo, an induction generator, or the like. The electrical power PA conveyed by the electric connections 208 to a rectifier 210. The rectifier 210 converts the electrical power PA in the form of alternating current to an electrical power PD in the form of direct current. The electrical power PD is conveyed to a voltage manager module 212 via the electric connections 208. The voltage manager module 212 may regulate an inverter 214. In an embodiment, the voltage manager module 212 may also receive an electrical power P1 from a thermoelectric controller 215. The details of the thermoelectric controller 215 will be described later. The electrical power P1 may be in the form of direct current. Further, the voltage manager module 212 may receive an electrical power PB from an energy storage system 220. The details of the energy storage system 220 will be explained later. The electrical power PB may be in the form of direct current. In an embodiment, the voltage manager module 212 may provide an electrical power P2 to an auxiliary system 218 of the vehicle 100. An electrical power P3 may be equal to a sum of the electrical powers PD, P1 and PB minus the electrical power P2. The electrical power P3 is provided to the inverter 214.

In an embodiment, the inverter 214 may convert the electrical power P3 into a drive power PW in the form of alternating current. The drive power PW is transmitted to the drive system 216 of the vehicle 100. The drive system 216 includes the traction motors which drive the vehicle 100. The drive power PW may be distributed among the traction motors. The inverter 214 may include one or more switching devices, for example, thyristors, insulated-gate bipolar transistors (IGBT), or the like in order to vary input frequency and/or voltage to the traction motors. Varying input frequency and/or voltage may vary speed and/or torque of the traction motors. The voltage manager module 212 may therefore control speed and/or torque of the traction motors via the inverter 214. Further, the drive power PW may change depending on a drive power requirement P4 associated with the drive system 216. The sum of the electrical powers PD, PB and P1, and hence the drive power PW may be sufficient to meet the drive power requirement P4 of the drive system 216. In an embodiment, the drive power requirement P4 may be indicated by a throttle position. There may be multiple throttle positions corresponding to discrete throttle notches Ni (i=1, 2, . . . , m). Each of the throttle notches Ni may correspond to a level of the power output PM of the engine 104. A higher throttle notch Ni may correspond to a higher level of the power output PM of the engine. The throttle notches Ni may be manually or automatically changed.

In an embodiment, the drive system 216 and the auxiliary system 218 may form part of an electrical equipment of the vehicle 100. The auxiliary system 218 may include various components of the vehicle 100, other than the drive system 216, that require electrical power, for example, the lights, pumps, electronic devices etc. The auxiliary system 218 also includes an energy storage system 220. In an embodiment, the energy storage system 220 may include one or more batteries. However, the energy storage system 220 may also include ultracapacitors without deviating from the scope of the present disclosure. An auxiliary power requirement P5 may be associated with the auxiliary system 218. An electrical power requirement P of the vehicle 100 may be a sum of the drive power requirement P4 and the auxiliary power requirement P5.

As shown in FIG. 2, in an embodiment, the thermoelectric controller 215 may receive the thermoelectric power PT from the thermoelectric module 202 via the electric connections 208. In an alternative embodiment (not shown), the thermoelectric power PT may be provided to the voltage manager module 212, and the voltage manager module 212 may regulate a distribution of the thermoelectric power PT based on control signals from the thermoelectric controller 215. The thermoelectric controller 215 may route at least a part of the thermoelectric power PT to the voltage manager module 212 in the form of the electrical power P1. Further, the thermoelectric controller 215 may route at least a part of the thermoelectric power PT to the auxiliary system 218 in the form of an electrical power P6. In an embodiment, a sum of the electrical powers P1 and P6 may be equal to the thermoelectric power PT. Further, a sum of the electric power P6, from the thermoelectric controller 215, and the electric power P2, from the voltage manager module 212, may be sufficient to meet the auxiliary power requirement P5. The auxiliary system 218 may include various inverters, rectifiers, voltage/frequency modulators, connectors etc. in order to distribute the electrical powers P2 and P6 to the various components of the auxiliary system 218.

As shown in FIG. 2, a data acquisition system 222 is configured to receive various input signals. In an embodiment, the data acquisition system 222 may be configured to receive input signals indicative of the values of various parameters, such as the auxiliary power requirement P5, the drive power requirement P4, the throttle notch Ni, a stored energy ES of the energy storage system 220, the engine speed S and the temperature difference DeltaT between the high temperature heat source TH and the low temperature heat source TL. The data acquisition system 222 may be connected to multiple sensors (not shown), and include multiple signal filters (not shown), converters (not shown), or the like to process the input signals in order to obtain the values of the parameters. The input signals indicative of the auxiliary power requirement P5 may include the power requirement of the individual components of the auxiliary system 218. Further, the power requirement of the individual components may be provided in terms of voltage and current values. The input signals indicative of the drive power requirement P4 may include the throttle notch Ni. Further, the drive power requirement P4 may also be provided in terms of voltage and current values. The thermoelectric controller 215 may be in communication with the data acquisition system 222, and may receive data including the values of the various parameters.

The thermoelectric controller 215 may be configured to provide control signals to the voltage manager module 212, and also regulate a usage of the thermoelectric power PT and the stored energy ES of the energy storage system 220 based on the data received from the data acquisition system 222.

In an embodiment, the thermoelectric controller 215 may be configured to control a parameter of the engine 104 to maintain an optimal value DeltaTopt of the temperature difference DeltaT between the high temperature heat source TH and the low temperature heat source TL. In a further embodiment, the parameter of the engine 104 may be the engine speed S. In another embodiment, the thermoelectric controller 215 may be configured to determine an optimal value Sopt of the engine speed S to attain the optimal value DeltaTopt of the temperature difference DeltaT based on the electrical power requirement P of the vehicle 100. The thermoelectric controller 215 may control the engine speed S by providing control signals to the voltage manager module 212. The voltage manager module 212 in turn may provide control signals to the engine controller 209. The engine controller 209 may control the engine speed S by regulating the fuel supply rate, the ignition timings, the valve timings etc. In an embodiment, the thermoelectric controller 215 may also determine whether the drive power requirement P4 is above a predetermined threshold Pmin. The predetermined threshold Pmin may be based on a predetermined throttle position. The predetermined throttle position may be equivalent to a threshold throttle notch Nmin. The predetermined threshold Pmin and the threshold throttle notch Nmin may be stored in the thermoelectric controller 215. Further, the thermoelectric controller 215 is configured to route at least a portion of the thermoelectric power PT to the drive system 216 when the drive power requirement P4 is equal to or above the predetermined threshold Pmin. In a further embodiment, the thermoelectric controller 215 may be configured to route the thermoelectric power PT to the auxiliary system 218 when the drive power requirement P4 is below the predetermined threshold Pmin. The thermoelectric controller 215 may maintain the optimal value DeltaTopt and determine the optimal value Sopt based on various strategies, as will be explained hereinafter.

In an example, the engine 104 may be running on a low throttle position, i.e., a low throttle notch Ni. The low throttle notch Ni may be lower than the threshold throttle notch Nmin. Consequently, the drive power requirement P4 may be lower than the predetermined threshold Pmin. The thermoelectric controller 215 may therefore provide the thermoelectric power PT to the auxiliary system 218. Thus, the electrical power P6 may be equal to the thermoelectric power PT. In a further example, if the auxiliary power requirement P5 is lower than the thermoelectric power PT, the remaining portion of the thermoelectric power PT may be routed to the energy storage system 220. The electrical power PB from the energy storage system 220 may be zero. Further, the electrical power P2 from the voltage manager module 212 may be zero as the auxiliary power requirement P5 is met by the thermoelectric power PT. Further, the electrical power P1, from the thermoelectric controller 215 to the voltage manager module 212, may also be zero as the thermoelectric controller 215 is providing the whole of the thermoelectric power PT to the auxiliary system 218.

At the low throttle notch Ni, the electrical power PD from the rectifier 210 may meet the drive power requirement P4. Therefore, the power output PM of the engine 104 may meet the drive power requirement P4. The engine controller 209 may maintain the engine 104 at the engine speed S at the optimal value Sopt in order to meet the drive power requirement P4. A temperature of the exhaust 116, and hence the temperature of the high temperature heat source TH may be at least partly dependent on the power output PM of the engine 104. Since, the power output PM of the engine 104 may depend at least partly on the engine speed S, the temperature of the high temperature heat source TH may be dependent on the engine speed S. Therefore, at the optimal value Sopt of the engine speed S, corresponding to the low throttle notch Ni, the temperature of the high temperature heat source TH may attain a particular value. In an embodiment, the thermoelectric controller 215 may control the temperature of the low temperature heat source TL such that the thermoelectric power PT corresponding to the temperature difference DeltaT may at least meet the auxiliary power requirement P5. The thermoelectric controller 215 may control the temperature of the low temperature heat source TL by regulating the flows of ambient air, and coolants of the cooling system and the secondary cooling system. Consequently, the temperature difference DeltaT may attain a particular value. In an embodiment, the temperature difference DeltaT, at the optimal value Sopt of the engine speed S, may be the optimal value DeltaTopt.

Alternatively, if the thermoelectric controller 215 regulates the temperature of the low temperature heat source TL such that the thermoelectric power PT is lower than the auxiliary power requirement P5, the electrical power P2 from the voltage manager module 212 may provide the balance. Further, the energy storage system 220 may not receive any power.

In another example, the throttle position associated the engine 104 changes to a high level, i.e., a high throttle notch Ni. The high throttle notch Ni may be higher than or equal to the threshold throttle notch Nmin. Consequently, the drive power requirement P4 may be higher than or equal to the predetermined threshold Pmin. The engine controller 209 may then increase the engine speed S to meet the high value of the drive power requirement P4. Consequently, the temperature of the exhaust 116 may increase. Consequently, the temperature difference DeltaT and the thermoelectric power PT may also increase. It may be apparent that there may be a time lag between any change in the engine speed S and the corresponding change in the temperature difference DeltaT. The time lag may be due to a temperature of the high temperature heat source TH to increase and thereby increase the temperature difference DeltaT. Therefore, the thermoelectric controller 215 may receive input signals regarding the increase in the temperature difference DeltaT and the thermoelectric power PT after the time lag. In an embodiment, the increased value of the thermoelectric power PT may be higher than the auxiliary power requirement P5. The thermoelectric controller 215 may route the balance to the voltage manager module 212 as the electrical power P1. Further, the thermoelectric controller 215 may route the electrical power PB from the energy storage system 220 to the voltage manager module 212. Therefore, the voltage manager module 212 may receive the electrical powers P1 and PB, in addition to the electrical power PD from the rectifier 210. Therefore, the electrical power P3, which is the sum of the electrical powers P1, PB and PD, may be higher than the drive power requirement P4. Consequently, the thermoelectric controller 215 may send control signals to the voltage manager module 212 to decrease the engine speed S to a lower value such that the sum of the electrical powers P1, PB and PD may be equal to the drive power requirement P4. However, due to the decrease in the engine speed S, the exhaust temperature, and hence the temperature difference DeltaT may decrease to a lower value after a time lag. Therefore, the thermoelectric power PT decreases, and the electrical power P1, from the thermoelectric controller 215 to the voltage manager module 212, also decreases. The thermoelectric controller 215 may then send control signals to increase the engine speed S in order to meet the drive power requirement P4. This may increase the temperature difference DeltaT and the thermoelectric power PT. The electrical power P1 may also increase.

In an embodiment, there may be multiple such iterations each of which involves the thermoelectric controller 215 increasing and decreasing the engine speed S in a cyclic manner. The aim of the iterations may be for the thermoelectric controller 215 to determine the optimal value Sopt of the engine speed S to attain the optimal value DeltaTopt of the temperature difference DeltaT when the engine 104 set at the high throttle notch Ni. At the optimal values DeltaTopt and Sopt, there may be a state of equilibrium with the thermoelectric controller 215 causing no further changes in the temperature difference DeltaT and the engine speed S. Further, at the optimal values Sopt and DeltaTopt, the drive power requirement P4 and the auxiliary power requirement P5 may be met with a minimum value of the power output PM of the engine 104. In another embodiment, the thermoelectric controller 215 may stop extracting the electrical power PB from the energy storage system 220 if the stored energy ES of the energy storage system 220 falls below a minimum level. The thermoelectric controller 215 may then carry out one or more iterations to arrive at a new set of the optimal values Sopt and DeltaTopt. In a further embodiment, the thermoelectric controller 215 may additionally regulate the temperature of the low temperature heat source TL in order to reach the optimal values Sopt and DeltaTopt.

The control strategies, as described above, are exemplary in nature, and the thermoelectric controller 215 may adopt any alternative control strategies to determine the optimal values Sopt and DeltaTopt for any setting of the throttle notch Ni.

FIG. 3 illustrates the thermoelectric module 202, according to an embodiment of the present disclosure. The thermoelectric module 202 includes multiple thermoelectric devices 302. Each of the thermoelectric devices 302 may be made of a semiconductor material, a metal alloy, or the like such that each of the thermoelectric devices 302 may generate a thermoelectric power based on the temperature difference DeltaT between the high temperature side 204 (shown in FIG. 2) and the low temperature side 206 (shown in FIG. 2) of the thermoelectric module 202. The thermoelectric power results in a DC voltage across each of the thermoelectric devices 302, thereby resulting in a current flow from a positive terminal (+) to a negative terminal (−) of each of the thermoelectric devices 302.

As shown in FIG. 3, a number of the thermoelectric devices 302 may be connected in series with a positive terminal of one thermoelectric device 302 connected to a negative terminal of the adjacent thermoelectric device 302 in order to form a series section 304. Each of the series sections 304, as shown in FIG. 3, includes four of the thermoelectric devices 302 connected in series. Further, there are four of the series sections 304. However, there may be any number of the thermoelectric devices 302 connected in series to form each of the series sections 304, and there may be any number of the series sections 304. The series sections 304 are connected to an output 306 of the thermoelectric module 202 via electric connectors 308 in a parallel configuration. The thermoelectric power PT may be provided at the output 306. The electric connectors 308 are connected to a positive side (+) and a negative side (−) of the output 306 of the thermoelectric module 202. Thus, a DC voltage across each of the four thermoelectric devices 302 is added to provide a voltage output of each of the series sections 304. However, the same current flows through each of the four thermoelectric devices 302 of the series section 304. The currents from each of the series sections 304 may get added in the electric connectors 308 and flow to the output 306. Thus, a voltage output of the thermoelectric module 202 may be the voltage output of each of the series sections 304. Further, a current output of the thermoelectric module 202 may be equal to a sum of the currents from the series sections 304. In an embodiment, a blocking diode (not shown) may be provided at one end of each of the series sections 304. The blocking diode may ensure a unidirectional flow of the current through each of the series sections 304. Therefore, any one of the series sections 304, which does not generate any thermoelectric power, may not draw current from any of the other series sections 304, and reduce the thermoelectric power PT generated by the thermoelectric module 202.

INDUSTRIAL APPLICABILITY

Current vehicles powered by an engine are provided with air and fuel mixture. The engine produces power by combusting the mixture of air and fuel. The engine generates an exhaust as a byproduct of combustion. The exhaust may be discharged after passing through the one or more turbochargers. Consequently, a heat associated with the exhaust may be wasted. Therefore, an efficiency of the vehicles may get reduced.

The present disclosure relates to the energy recovery system 200 for the vehicle 100 powered by the engine 104. The vehicle 100 may be a locomotive. Alternatively, the vehicle may be a diesel-electric multiple unit. The vehicle 100 includes a heat source that generates waste heat. In an embodiment, the heat source may be the exhaust 116. The thermoelectric module 202 is interfaced with the heat source. The waste heat from the exhaust 116 provides the high temperature heat sources TH for the thermoelectric module 202. Further, the low temperature heat source TL is interfaced with the thermoelectric module 202. The temperature difference DeltaT between the high temperature heat source TH and the low temperature heat source TL produce the thermoelectric power PT. The thermoelectric controller 215 is configured to control the engine speed S to maintain the optimal value DeltaTopt of the temperature difference DeltaT. The thermoelectric controller 215 may be further configured to determine the optimal value Sopt of the engine speed to attain the optimal value DeltaTopt of the temperature difference based on the electrical power requirement P of the vehicle 100.

FIG. 4 illustrates a method 400 of energy recovery in the vehicle 100 powered by the engine 104, according to an aspect of the present disclosure. At step 402, the method 400 includes interfacing the thermoelectric module 202 with the heat source of the vehicle 100. The heat source generates waste heat, which provides the high temperature heat source TH for the thermoelectric module 202. In an embodiment, the heat source is the exhaust 116 generated by the engine 104. At step 404, the method 400 includes interfacing the low temperature heat source TL with the thermoelectric module 202. The temperature difference DeltaT between the high temperature heat source TH and the low temperature heat source TL produces the thermoelectric power PT. At step 406, the method 400 includes controlling a parameter of the engine 104 to maintain the optimal value DeltaTopt of the temperature difference DeltaT.

In an embodiment, the parameter of the engine 104 may be the engine speed S. The method 400 may further include determining the electrical power requirement P of the vehicle 100. The method 400 may also include determining the optimal value Sopt if the engine speed S to attain the optimal value DeltaTopt of the temperature difference DeltaT. In an embodiment, the thermoelectric controller 215 may be configured to arrive at the optimal values DeltaTopt and Sopt after multiple iterations. The optimal values DeltaTopt and Sopt may correspond to a particular throttle notch Ni. At the optimal values DeltaTopt and Sopt, there may be a state of equilibrium with the thermoelectric controller 215 causing no further changes in the temperature difference DeltaT and the engine speed S. Further, at the optimal values Sopt and DeltaTopt, the electrical power requirement P may be met with a minimum value of the power output PM of the engine 104.

In an embodiment, the electrical power requirement P may include the drive power requirement P4 and the auxiliary power requirement P5. The method 400 may further include determining whether the drive power requirement P4 is above the predetermined threshold Pmin. The method 400 may include routing at least a portion of the thermoelectric power PT to the drive system 216 when the drive power requirement P4 is equal or above the predetermined threshold Pmin. The method 400 further includes routing the thermoelectric power PT to the auxiliary system 218 when the drive power requirement P4 is below the predetermined threshold Pmin.

Thus, energy recovery system 200 the method 400 of energy recovery may increase an efficient of the vehicle 100 as the thermoelectric power PT may provide at least partly the electrical power requirement P of the vehicle 100. Specifically, the thermoelectric controller 215 may iteratively arrive at the optimal values DeltaTopt and Sopt at a particular throttle notch Ni such that the electrical power requirement P may be met with a minimum value of the power output PM of the engine 104. Therefore, a fuel consumption of the engine 104 may be minimized. Moreover, the thermoelectric controller 215 may also store a part of the thermoelectric power PT in the energy storage system 220 at a low throttle notch Ni and hence, a low value of the drive power requirement P4. The thermoelectric controller 215 may utilize the stored energy ES of the energy storage system 220 at a high throttle notch Ni, and hence a high value of the drive power requirement P4. Therefore, the thermoelectric power PT may be optimally used based on the electrical power requirement P of the vehicle 100.

While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof. 

What is claimed is:
 1. An energy recovery system for a vehicle powered by an engine comprising: a thermoelectric module interfaced with a heat source of the vehicle, wherein the heat source generates waste heat, and wherein the waste heat provides a high temperature heat source for the thermoelectric module; a low temperature heat source interfaced with the thermoelectric module, wherein a temperature difference between the high temperature heat source and the low temperature heat source produces a thermoelectric power; and a controller configured to control a parameter of the engine to maintain an optimal value of the temperature difference between the high temperature heat source and the low temperature heat source.
 2. The energy recovery system of claim 1, wherein the parameter of the engine includes an engine speed.
 3. The energy recovery system of claim 2, wherein the controller is configured to determine an optimal value of the engine speed to attain the optimal value of the temperature difference between the high temperature heat source and the low temperature heat source based on an electrical power requirement of the vehicle.
 4. The energy recovery system of claim 3, wherein the electrical power requirement of the vehicle includes a drive power requirement associated with a drive system of the vehicle and an auxiliary power requirement associated with an auxiliary system of the vehicle.
 5. The energy recovery system of claim 4, wherein controller is further configured to determine whether the drive power requirement is above a predetermined threshold, and wherein the controller is configured to route at least a portion of the thermoelectric power to the drive system when the drive power requirement is equal to or above the predetermined threshold.
 6. The energy recovery system of claim 5, wherein the controller is further configured to route the thermoelectric power to the auxiliary system when the drive power requirement is below the predetermined threshold.
 7. The energy recovery system of claim 4, wherein the drive power requirement is indicated by a throttle position, and wherein the predetermined threshold of the drive power requirement is based on a predetermined throttle position.
 8. The energy recovery system of claim 4, wherein the auxiliary system includes an energy storage system.
 9. A locomotive powered by an engine comprising: a heat source generating waste heat; a thermoelectric module interfaced with the heat source, wherein the waste heat provides a high temperature heat source for the thermoelectric module; a low temperature heat source interfaced with the thermoelectric module, wherein a temperature difference between the high temperature heat source and the low temperature heat source produces a thermoelectric power; and a controller configured to control a parameter of the engine to maintain an optimal value of the temperature difference between the high temperature heat source and the low temperature heat source.
 10. The locomotive of claim 9, wherein the parameter of the engine includes an engine speed.
 11. The locomotive of claim 10, wherein the controller is configured to determine an optimal value of the engine speed to attain the optimal value of the temperature difference between the high temperature heat source and the low temperature heat source based on an electrical power requirement of the vehicle.
 12. The locomotive of claim 11, wherein the electrical power requirement of the vehicle includes a drive power requirement associated with a drive system of the vehicle and an auxiliary power requirement associated with an auxiliary system of the vehicle.
 13. The locomotive of claim 12, wherein controller is further configured to determine whether the drive power requirement is above a predetermined threshold, and wherein the controller is configured to route at least a portion of the thermoelectric power to the drive system when the drive power requirement is equal to or above the predetermined threshold.
 14. The locomotive system of claim 13, wherein the controller is further configured to route the thermoelectric power to the auxiliary system when the drive power requirement is below the predetermined threshold.
 15. The locomotive of claim 12, wherein the drive power requirement is indicated by a throttle position, and wherein the predetermined threshold of the drive power requirement is based on a predetermined throttle position.
 16. The locomotive of claim 12, wherein the auxiliary system includes an energy storage system.
 17. A method of energy recovery in a vehicle powered by an engine, the method comprising: interfacing a thermoelectric module with a heat source of the vehicle, wherein the heat source generates waste heat; and wherein the waste heat provides a high temperature heat source for the thermoelectric module; interfacing a low temperature heat source with the thermoelectric module, wherein a temperature difference between the high temperature heat source and low temperature heat source produces a thermoelectric power; and controlling a parameter of the engine to maintain an optimal value of the temperature difference between the high temperature heat source and the low temperature heat source.
 18. The method of claim 17, wherein the parameter of the engine include an engine speed, the method further comprising: determining an electrical power requirement of the vehicle; and determining an optimal value of the engine speed to attain the optimal value of the temperature difference between the high temperature heat source and the low temperature heat source based on the power requirement of the vehicle.
 19. The method of claim 18, wherein the electrical power requirement of the vehicle includes a drive power requirement associated with a drive system of the vehicle and an auxiliary power requirement associated with an auxiliary system of the vehicle, the method further comprising: determining whether the drive power requirement is above a predetermined threshold; and routing at least a portion of the thermoelectric power to the drive system when the drive power requirement is equal to or above the predetermined threshold.
 20. The method of claim 19 further comprising: routing the thermoelectric power to the auxiliary system when the drive power requirement is below the predetermined threshold. 